2. Changes to
population size
• Adding & removing individuals
from a population
• birth
• death
• immigration
• emigration
2005-2006
3. Growth rate
• Exponential growth
• characteristic of a population without limiting factors
• ex. introduced to a new environment
Whooping crane African elephant
coming back from near extinction protected from hunting
2005-2006
4. Carrying capacity
• Can populations continue to grow
exponentially?
• of course NOT!
• what sets limit?
• resources, predators, parasites
• Carrying Capacity (K)
• maximum population
size that environment
can support with no degradation of
habitat
• not fixed; varies with
changes in resources
2005-2006
5. Model of growth
Decrease in rate of growth as reach carrying capacity
2005-2006
6. Different life strategies
• K-selection
• r-selection
K-selection
mortality constant
r-selection
2005-2006
7. Reproductive strategies
• K-strategy
• have few offspring & invest a lot of energy in
raising them to reproductive age
• primates
• coconut
• r-strategy
• have many offspring & invest little in their
survival
• insects
• dandelion & other weeds
2005-2006
9. Age structure
• Relative number of individuals of each age
What do the data imply about population growth in these
countries?
2005-2006
10. Human population
What factors have contributed to this exponential
growth pattern?
2005→6 billion
Is the human
population reaching
carrying capacity?
1650→500 million
2005-2006
17. Trophic structure
• Food chains
• feeding relationships
• food chain usually 4 or 5 links =
trophic levels
• length of food chain limited by
inefficiency of energy transfer
2005-2006
18. Energy transfer
• Energy in
• from the Sun
• captured by autotrophs =
producers (plants)
• Energy through
• food chain
• transfer of energy
from autotrophs to
heterotrophs
(herbivores to carnivores)
• heterotrophs = consumers
• herbivores
• carnivores
2005-2006
20. Pyramids of production
• represent the loss of energy from a food chain
• how much energy is turned into biomass
2005-2006
21. Food webs
• Food chains are hooked
together into food webs
• Who eats whom?
• a species may weave
into web at more than 1
trophic level
• bears
• “there’s always a bigger
fish”
What limits the length of
a food chain? 2005-2006
22. Implications
• Dynamics of energy through ecosystems have
important implications for human populations
• what food would be more ecologically sound?
2005-2006
23. Disturbances
• Most communities are in a state of
change due to disturbances
• fire, weather, human activities, etc.
• not all are negative
2005-2006
25. Different life strategies
• K-selection
• r-selection
K-selection
mortality constant
r-selection
2005-2006
26. Reproductive strategies
• K-strategy
• have few offspring & invest a lot of energy in
raising them to reproductive age
• primates
• coconut
• r-strategy
• have many offspring & invest little in their
survival
• insects
• dandelion & other weeds
2005-2006
28. Age structure
• Relative number of individuals of each age
What do the data imply about population growth in these
countries?
2005-2006
29. Human population
2005→6 billion
What factors have contributed to this exponential
growth pattern?
Is the human
population reaching
carrying capacity?
1650→500 million
2005-2006
36. Trophic structure
• Food chains
• feeding relationships
• food chain usually 4 or 5 links =
trophic levels
• length of food chain limited by
inefficiency of energy transfer
2005-2006
37. Energy transfer
• Energy in
• from the Sun
• captured by autotrophs =
producers (plants)
• Energy through
• food chain
• transfer of energy
from autotrophs to
heterotrophs
(herbivores to carnivores)
• heterotrophs = consumers
• herbivores
• carnivores
2005-2006
39. Pyramids of production
• represent the loss of energy from a food chain
• how much energy is turned into biomass
2005-2006
40. Food webs
• Food chains are hooked
together into food webs
• Who eats whom?
• a species may weave
into web at more than 1
trophic level
• bears
• “there’s always a bigger
fish”
What limits the length of
a food chain? 2005-2006
41. Implications
• Dynamics of energy through ecosystems have
important implications for human populations
• what food would be more ecologically sound?
2005-2006
42. Disturbances
• Most communities are in a state of
change due to disturbances
• fire, weather, human activities, etc.
• not all are negative
2005-2006
44. Ecological cycle
fire as part of a natural community cycle
2005-2006
45. Ecological succession
• The sequence of community changes after a disturbance
• transition in species composition over ecological time
• years or decades
Mt. St. Helens 2005-2006
46. Successionover time
Change in species mix
• From bare soil,
then…
{
• bacteria
make
soil • lichens & mosses
• grasses
• shrubs
• trees
2005-2006
47. Succession
from mosses & lichens
= pioneer species
to shrubs & trees
2005-2006
48. Climax forest
The species mix of
climax forest is
dependent on the
abiotic factors of the
region
solar energy levels
temperature
rainfall
fertility & depth of soil
2005-2006
birch, beech, maple, hemlock
Editor's Notes
The J–shaped curve of exponential growth is characteristic of some populations that are introduced into a new or unfilled environment or whose numbers have been drastically reduced by a catastrophic event and are rebounding. The graph illustrates the exponential population growth that occurred in the population of elephants in Kruger National Park, South Africa, after they were protected from hunting. After approximately 60 years of exponential growth, the large number of elephants had caused enough damage to the park vegetation that a collapse in the elephant food supply was likely, leading to an end to population growth through starvation. To protect other species and the park ecosystem before that happened, park managers began limiting the elephant population by using birth control and exporting elephants to other countries.
The population doubled to 1 billion within the next two centuries, doubled again to 2 billion between 1850 and 1930, and doubled still again by 1975 to more than 4 billion. The global population now numbers over 6 billion people and is increasing by about 73 million each year. The population grows by approximately 201,000 people each day, the equivalent of adding a city the size of Amarillo, Texas, or Madison, Wisconsin. Every week the population increases by the size of San Antonio, Milwaukee, or Indianapolis. It takes only four years for world population growth to add the equivalent of another United States. Population ecologists predict a population of 7.3–8.4 billion people on Earth by the year 2025.
We consume more than just food: water, energy, space/habitat
The population doubled to 1 billion within the next two centuries, doubled again to 2 billion between 1850 and 1930, and doubled still again by 1975 to more than 4 billion. The global population now numbers over 6 billion people and is increasing by about 73 million each year. The population grows by approximately 201,000 people each day, the equivalent of adding a city the size of Amarillo, Texas, or Madison, Wisconsin. Every week the population increases by the size of San Antonio, Milwaukee, or Indianapolis. It takes only four years for world population growth to add the equivalent of another United States. Population ecologists predict a population of 7.3–8.4 billion people on Earth by the year 2025.
We consume more than just food: water, energy, space/habitat
